Smokestack with vibration damper

ABSTRACT

A free-standing chimney stack having a pair of spaced integral tubular metal shells and means to support the shells on a base. The shells have mutual frictional engagement through spring stabilizer guides located near the top of the stack. The stabilizer guides are preloaded by adjustment of the springs to produce predetermined frictional bearing pressures, thereby to increase the internal damping of the structure so that for a critical wind speed the resulting vibration is held to a minimum.

451 Apr. 17, 1973 United States Patent 1191 Roy 3,669,042 6/1972 Lawrence............ .1 10/184 SMOKESTACK WITH VIBRATION DAMPER R0 Box J, Newton Primary Examiner-Kenneth W. slfirggue 6 Inventor: Assistant Examiner-James C. Ye

Attorney-Herbert W. Kenway et [22] Filed: Dec. 10, 1971 [21] Appl. N0.: 206,849

e r na mee r onw ot P a UCC S n0 o 1. mwm t u ug A free the top of the stack. The stabilizer guides are preloaded by adjustment of the springs to produce 00 5 43 829 IF; w I 1 m 0 Ya mm" n ne mm L C d S M U.mF HUN 555 References Cited predetermined frictional bearing pressures, thereby to UNITED STATES PATENTS increase the internal damping of the structure so that i for a critical wind speed the resulting vibration is held to a minimum.

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98/60 ...1 10/184 11/1970 10/184 16 Claims, 6 Drawing Figures 2,604,838 7/1952 3,368,506 2/1968 Lawrence...... 3,537,41 l

BRIEF SUMMARY OF THE INVENTION This invention relates generally to upright stacks for the vertical transmission of flue gases to the atmosphere. The gases may be the products of various industrial processes and are typically the products of combustion from furnaces associated with boilers or incinerators. More particularly, the invention relates to means for increasing the tolerance of the stack to the effects of wind loading, particularly caused by vibrations induced by Karman vo'rtices.

A principal object of this invention is to provide a stack having the features and advantages described in my US. Pat. No. 3,537,411, dated Nov. 3, 1970, and including means to increase the tolerance of the stack against wind loading. Stacks of this general type are of dual tubular steel shell construction, and derive certain advantages from the thermal insulating properties of the space between the two shells. The necessity for thermal insulation in such stacks is described in said patent and is now well understood in the art. It has the object of reducing the formation of corrosive acidic and soot-agglomerating condensates on the inner wall of the stack.

Dual shell steel stacks have been constructed in a variety of ways. They may be guyed for support or freestanding; they may be composed of a number of verti' cally stacked sections bolted or welded together endto-end, or of essentially integral, single-shelled construction as described in said patent; and they may be constructed with the weight of the stack substantially supported by the outer shell, by the inner shell, or by both shells in varying proportions. Depending upon the particular construction, the effects of wind loading on the stack include deflection, vibration and the production of stresses in the walls of one or both shells. In extreme cases this may result in fatigue cracking of the shells at the critical wind velocity of the stack. It is well known that wind impinging on a stack with a horizontal component of force produces so-called Karman vortices that tend to result in stack vibrations and also distortion of the cross section of the stack, or so-called ovalling.

It is an object of this invention to provide means for dissipating any vibrational energy in the stack, as by converting such energy into heat.

This invention achieves the foregoing object by provision of one or more frictional stabilizer guide sets situated between the inner and outer shells, which act as vibration dampers. These guide sets have provision for frictional engagement'with one of the shells through the action of adjustable springs mounted on the other shell. A set of stabilizer guides is preferably mounted near the top of the stack and in some cases also at lower positions, with the inner and outer shells both supported on the base in either case, either at their lower ends or at points between their lower ends and the breeching. The resilient frictional interconnection of the inner and outer shells provides a composite structure which has greater internal damping than either shell considered as an independent structure. By appropriate adjustment of the springs it is possible to achieve optimum damping by dissipation of vibrational energy through heat.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is an elevation of a stack embodying the invention, partly in section.

FIG. 2 is an elevation in section showing details of the mounting at the base of the stack.

FIG. 3 is an elevation in section showing details of a stabilizer guide.

FIG. 4 is a partial plan view in section taken on line 4-4 of FIG. 3.

FIG. 5 is a partial elevation in section showing details of the alignment guide and bellows expansion joint in the embodiment of FIG. 1.

FIG. 6 is a partial elevation in section of an alternative embodiment employing a slip expansion joint in place of the bellows joint of FIGS. II and 5.

DETAILED DESCRIPTION Referring to the embodiment of FIGS. 1 to 5, a stack embodying the invention is generally designated at 12, and includes an outer, integral sheet steel shell 14 spaced from an inner, integral sheet steel shell 16. The top of the stack comprises a cone portion 18. Below this portion the shells may both be of cylindrical shape from end to end, although on some stacks a lower portion of each shell may be flared outwardly toward the base for added structural stability. Each shell is metallurgically one integral piece from end to end, formed of corrosion-resistant, high-strength steel plates, the plates being curved to the appropriate radius and joined along girth and staggered vertical seams by continuous full penetration butt welds, as fully described in my above-mentioned U.S. Pat. No. 3,537,411. The shells are thereby formed into cylindrical columns, with the circular cross section of the inner shell 16 being of sufficiently smaller diameter than that of the outer shell 14 to form an appreciable space 20 when assembled concentrically as shown.

The illustrated stack is freestanding; that is, it is ordinarily completely supported by a concrete foundation 22 (FIG. 2) with no laterally supporting guy wires attached to it above the foundation. The lower portion of the stack is typically housed within a building and passes through a roof top at some point above a breeching opening 24 with provision for the usual roof thimble and rain collar, not shown; but the stack is not necessarily supported significantly by the roof, the breeching structure or the frame of the building.

The shells 14 and 16 are welded to a circular steel plate base ring 26 (FIG. 2), and the outer shell 14 is also welded to a circular steel ring 28 spaced from the ring 26. Angularly spaced between the rings 26 and 28 are a number of steel gussets 30, each welded to both rings, and the rings have aligned holes to receive anchor bolts 32 between the gussets. The bolts 32 pass through pipe sleeves 34 embedded :in the concrete 22, and are anchored by means of washers 36 and bolt heads 38 or nuts welded to the washers and performing a similar function. Grouting 40 serves to level the base ring 26 so that the stack will be plumb, and this grouting is preferably tapered toward a suitable drain hole 42. This base supporting structure is in other respects essentially identical to that described in the abovementioned patent, to which reference is made for further details.

Circular angle rings 44 are welded to the inner surface of the outer shell 14 at uniform, longitudinally spaced intervals, the spacing between adjacent rings preferably being equal approximately to one and onehalf times the outer diameter of the shell 14. The downwardly-depending flanges of the rings 44 are spaced from the outer surface of the inner shell 16 as assembled, thereby avoiding connections between the shells at these rings under all conditions except in cases of extreme wind load deflection. One of the functions of these rings is to stiffen the outer shell to prevent it from ovalling under wind load. Another function is to provide supports for sets of stabilizer guides 46, details of which are given below.

A breeching structure 48, which may be formed in the manner described in my above-mentioned patent or in any other suitable manner, passes through the shell 14 and is connected to a flue space 50 within the inner shell 16.

The upper end of the outer shell 14 is butt welded at a girth seam 52 to a conical shaped plate steel outer cone 54. The upper end of the inner shell 16 terminates below the seam 52 at a point 56 (FIGS. 1 and located above the topmost angle ring 44. A circular ring-shaped steel top ring 58 is welded to the cone 54 and to a conical shaped plate steel inner cone 60, by continuous seal welds. A short cylindrical steel piece 61 is also welded to the cone 60. The member 60 preferably has a diameter at the bottom equal to that of the inner shell 16. The members 16 and 60 are longitudinally spaced and interconnected by a bellows expansion joint designated generally at 62. This joint comprises a metal bellows 64 having its ends factory welded to annular rings 66 and 68. These rings are respectively welded to telescoping cylindrical sleeves 70 and 72 having a close sliding fit to protect the bellows from the products of combustion and any condensates that may form on the upper inner flue walls.

The cones 54 and 60 in the cone portion 18 of the stack are provided with alignment guide means designated generally at 74. These means comprise a plurality of uniformly annularly spaced sets each consisting of a short, vertically oriented H-beam 76 welded to the outer shell and a short, vertically-oriented channel beam 78 welded to the member 60 and received with clearance in the space between the inwardly-projecting flanges of the beam 76. Thus the alignment guide means serve to prevent mutual disalignment of the members 54 and 60 while accommodating relative longitudinal movements between these members.

It will be noted that the above-described structure permits the space between the shells l4 and 16 to be continuous between the bottom and top of the stack as terminated by the base ring 26 and the top ring 58, and to be hermetically sealed by continuous seal welds at all joints. In view of the exposure of the stack to extreme temperature gradients and shocks, it has been found desirable to provide a combination pressure relief valve and vacuum breaker 80 connecting this space with the ambient space surrounding the stack. Preferably, this valve is adapted to vent air from the space 20 when the pressure differential between this space and the ambient space is above a first selected value, and also to draw air into the space 20 from the ambient space when the pressure differential between these spaces is above a second predetermined value, these values being separately adjustable although not necessarily of differing values, in a manner well understood in the art.

In some cases, it is not necessary for the space between the shells to be hermetically sealed, in which case a simple slip joint between the inner and outer shells is sufficient. This is illustrated in the alternative embodiment of FIG. 6. In this embodiment there is provided an outer shell 14 like the shell 14 of FIGS. 1 t0 5 welded to an outer cone 54', the latter forming a part of a cone portion 18 substantially as described in relation to FIG. 1. Circular ring plates 82, 84 and 86 are welded to a cylindrical member 88, the shell 14' and an inner cone 60', the member 88 having a loose sliding fit with the outer surface of an inner shell 16 at the upper end thereof, this shell being otherwise constructed like the shell 16 of FIGS. 1 to 5.

In many cases it is desirable to insulate the outer shell 14 or to provide an acid resistant lining on the inner shell 16, or both, as illustrated in FIG. 1. In such cases the inner face of the outer shell is covered by a blanket 90 of low conductivity, high temperature resistant spun fiberglas, which may be covered on the surface facing the space 20 by a galvanized poultry netting or similar material or by aluminum foil, or both. The blanket and covering netting or foil may be fastened to the outer shell by means of studs 92 over which they are impailed, being fastened to the studs by means of suitable clips 94. The addition of the blanket 90 to the space 20 increases the insulating properties already inherent in the latter. The flue side of the inner shell 16 is lined throughout its full height with a heat and acid resistant concrete material such as monocalcium aluminate mixed in a castable cement having the desired proper ties. To apply this lining, a suitable wire fabric 98 is fastened on anchor studs 100, and the lining 96 is applied through and over the wire fabric and cured by techniques commonly employed in the industry for cement lined steel chimney flues.

It will be noted that none of the structural elements makes a direct physical connection between the outer and inner shells 14 and 16, except at the base ring 26 and the stabilizer guides 46. Each set of guides comprises a plurality of uniformly annularly spaced guides encircling the inner shell. One set only of such guides may be provided near the top of the inner shell 16 at the uppermost location shown, or more than one sets may be provided as illustrated, in which case one set is located at the uppermost location shown. Details of the guide structure are shown in FIGS. 3 and 4. A number of slotted angle brackets 102 are bolted in equally spaced relation around an angle ring 44 by means of bolts 104. Slots 106 in the brackets extend radially of the stack to permit independent radial adjustment of each bracket during preloading as described below. A steel leaf spring 108 is welded at one end to an upstanding flange on each bracket 102 and has a steel wear plate 110 welded to its upper end. The plate 110 bears upon and frictionally engages a cylindrical steel friction ring 112 welded to the outer face of the inner shell 16. When the temperature within the flue space 50 equals the ambient temperature, the wear plate 110 bears upon the friction ring 112 near its upper end. The ring 112 extends a sufficient distance downwardly from that end to accommodate maximum flue temperature conditions during which the upper end 56 of the inner shell 16 is displaced upwardly relatively to the outer shell 14 as a result of thermal expansion, as described in the above-mentioned patent.

FIGS. 3, 4 and 5 show an alignment bolt 114 threaded into a nut 116, the nut being welded to the inner face of the inner shell 16 and the bolt passing through a clearance hole in the shell 16. A number of such alignment bolts are uniformly annularly spaced around each angle ring 44 to which a set of stabilizer guides is bolted. In practice, the entire stack is typically manufactured and assembled in the factory and the alignment bolts are adjusted as shown to space the inner shell 16 in exactly concentric relationship to the outer shell 14. After the shells have been aligned in this I manner, the springs 108 are preloaded. The purpose of the preloading operation is to cause the wear plates 110 to apply equal radial forces to the friction ring 112, whereby the magnitude of the net radial force will be zero and a predetermined resilient frictional coupling will interconnect the shells l4 and 16. The desired friction force per wear plate is first determined by calculation. The correct radial position of each bracket 102 is then determined as a function of the constant of the spring 108. With the alignment bolt 114 in the original position shown, the nut 1l8on the bolt is loosened and a hydraulic jack is placed between surfaces 120 and 122. The bracket 102 is thereby moved to deflect the lower end of the spring to a predetermined position as at 124 (FIG. 3), and the nut 118 is then tightened against a lock washer. 126. All of thesprings 108 around the angle ring 44 are equally preloaded in the manner described.

The above-described preloading operation is preferably carried out in the factory. After the stack has been erected upon and bolted to the foundation 22, the alignment bolts 114 are removed and replaced by shorter stud bolts that do not engage the angle ring 44 and serve in use only to seal the threaded holes in the nuts 116.

It will be understood that the preloading operation may be accomplished either by jacking each bracket to a position with a predetermined measured spacing between the surfaces 120 and 122 based upon the known spring constant of the leaf spring 108, or the jack may be advanced until a predetermined measured force has been imparted to the lower end of each spring. in either case, it will be apparent that larger spring forces result in greater frictional engagement of the inner and outer shells.

By the foregoing means each set of stabilizer guides 46 operates as a vibration damper, dissipating as heat at the wear plates 110 and engaging surfaces of the friction ring 112 the vibrational energy resulting from differential longitudinal deflections of the inner and outer shells.

As stated above, at least one set of stabilizer guides 46 is preferably provided near the top of the inner shell 16, and one or more additional sets may or may not be installed at lower positions along the stack. It will be evident that if other sets of stabilizer guides are used, suitable provision is made for access to preload the springs. This may be done through adjacent access ports located in the outer shell wall (not shown), or by making the spring adjustments on the lower sets during assembly of the stack and before completion of the adjacent girth seams in the inner and outer shells.

Other variations in the structure, fabrication and adjustments of the stack may also be accomplished to meet particular end use and installation requirements, without departing from the spirit and scope of this invention.

lclaim:

1. A chimney stack having, in combination,

an integral tubular metal outer shell,

an integral tubular metal inner shell within and spaced from the outer shell,

support means for vertical support of the shells at positions located at substantial distances from the upper ends thereof,

and vibration damper means vertically spaced from and above the support means, and extending from one shell into frictional engagement with the other shell.

2. A chimney stack according to claim 1, in which the vibration damper means apply a resilient frictional force to said other shell.

3. A chimney stack according to claim 2, in which the vibration damper means has provision to adjust the frictional force.

4. A chimney stack according to claim 3, in which the frictional force is adjusted to have a zero net vector horizontally on either shell when the stack is freestanding under no wind load.

5. A chimney stack according to claim 2, in which the vibration damper means includes a plurality of spring means annularly spaced about the shells.

6. A chimney stack according to claim 1, in which the vibration damper means are located near the upper ends of the shells.

7. A chimney stack according to claim 1, which is free-standing.

8. A chimney stack according to claim 1, in which the outer shell is free standing and the vibration damper means are adapted to transfer a portion of the wind load to the inner shell.

9. A chimney stack according to claim 1, with breather valve means venting the space between the shells, said space being otherwise sealed.

10. A chimney stack according to claim 9, in which the breather valve permits air to move into or out of said space at predetermined differentials between the pressure therein and the ambient pressure.

11. A chimney stack according to claim 1, with an expansion joint between the shells above the vibration damper means to accommodate differential vertical thermal expansion between the shells.

12. A chimney stack according to claim 11, in which the expansion joint includes a bellows having one end connected to the inner shell and the other end connected to the outer shell.

13. A chimney stack according, to claim 1, with a breeching located at least as high as the support means.

14. A chimney stack having, in combination,

an integral tubular metal outer shell,

an integral tubular metal inner shell within and spaced from the outer shell,

a breeching communicating with the inner shell,

support means for vertical support of the shells at positions located at least as close to the bottom ends thereof as the breeching,

each stabilizer guide means includes a bracket attached to one shell and means for attaching an end of the spring adjustably to the bracket to vary the frictional engagement with the other shell.

16. A chimney stack according to claim 15, in which the springs are leaf springs. 

1. A chimney stack having, in combination, an integral tubular metal outer shell, an integral tubular metal inner shell within and spaced from the outer shell, support means for vertical support of the shells at positions located at substantial distances from the upper ends thereof, and vibration damper means vertically spaced from and above the support means, and extending from one shell into frictional engagement with the other shell.
 2. A chimney stack according to claim 1, in which the vibration damper means apply a resilient frictional force to said other shell.
 3. A chimney stack according to claim 2, in which the vibration damper means has provision to adjust the frictional force.
 4. A chimney stack according to claim 3, in which the frictional force is adjusted to have a zero net vector horizontally on either shell when the stack is free-standing under no wind load.
 5. A chimney stack according to claim 2, in which the vibration damper means includes a plurality of spring means annularly spaced about the shells.
 6. A chimney stack according to claim 1, in which the vibration damper means are located near the upper ends of the shells.
 7. A chimney stack according to claim 1, which is free-standing.
 8. A chimney stack according to claim 1, in which the outer shell is free standing and the vibration damper means are adapted to transfer a portion of the wind load to the inner shell.
 9. A chimney stack according to claim 1, with breather valve means venting the space between the shells, said space being otherwise sealed.
 10. A chimney stack according to claim 9, in which the breather valve permits air to move into or out of said space at predetermined differentials between the pressure therein and the ambient pressure.
 11. A chimney stack according to claim 1, with an expansion joint between the shells above the vibration damper means to accommodate differEntial vertical thermal expansion between the shells.
 12. A chimney stack according to claim 11, in which the expansion joint includes a bellows having one end connected to the inner shell and the other end connected to the outer shell.
 13. A chimney stack according to claim 1, with a breeching located at least as high as the support means.
 14. A chimney stack having, in combination, an integral tubular metal outer shell, an integral tubular metal inner shell within and spaced from the outer shell, a breeching communicating with the inner shell, support means for vertical support of the shells at positions located at least as close to the bottom ends thereof as the breeching, and vibration damper means vertically spaced from and above the support means and comprising a plurality of stabilizer guide means annularly spaced between the shells, each stabilizer guide means including a spring and means attached to one end of the spring for frictionally engaging the wall of a shell.
 15. A chimney stack according to claim 14, in which each stabilizer guide means includes a bracket attached to one shell and means for attaching an end of the spring adjustably to the bracket to vary the frictional engagement with the other shell.
 16. A chimney stack according to claim 15, in which the springs are leaf springs. 